The present invention is directed to an apparatus for injection molding. More specifically, the disclosed apparatus allows for reduced injection cycle time when injecting rubber.
Injection molding presses for injecting molding materials into molds are well known in the manufacturing industry. Molding materials such as rubber composites must typically be cured within their molds under specific temperature and pressure conditions. Prior to the injection of molding material into the mold, the injection press clamps the mold so that the mold is under pressure during the injection operation.
The time required for each molding cycle may be six minutes or more. A molding cycle typically includes the steps of clamping the mold, injecting material into the mold, holding the mold in a clamped condition with the injection nozzle still contacting the mold to initiate curing, and recharging the injection unit with material. Such molding cycle times are required, since the molds must remain under pressure within the press to complete the injection operation, initiate curing, and recharge the injection unit with molding material for the next cycle. Recharging of the unit with material occurs during this time in order to prevent any loss of material from the unit and so that when the next mold is presented to the unit for filling, filling may be immediately begin.
U.S. Pat. No. 5,286,186 discloses an apparatus for injection molding rubber. The apparatus has both a check valve to prevent molding material from passing back into the extruder during injection of the material and a separate shut-off valve to prevent molding material from passing to the injection nozzle during recharging of the internal cavity. The check valve and the shut-off valve do not operate together such that when one is activated the other is automatically operated and material may still pass through one of the valves when not desired.
The present invention provides a new and improved apparatus for performing a molding process. The apparatus is designed to increase the number of molds processed in a specific time period by permitting recharging of the injection molding machine on the fly.
The injection molding machine has an extruder for providing molding material, a cavity for retaining the molding material prior to injection into a mold, a plunger within the cavity to move the material out of the cavity, and a check valve. The check valve has separate means to permit the material to flow from the extruder to the cavity and from the cavity to an adjacent mold.
The check valve has an injection outlet port to permit flow from the cavity to an injection nozzle and a transfer column to permit flow from the extruder to the cavity. The injection outlet port and the transfer column are spaced from one another.
Movement of the check valve from a recharging position to an injecting position is activated by a hydraulic cylinder. The check valve is moved axially along its centerline to move the valve from an injecting position to a recharging position.